For example, Patent Document 1 discloses a method of preventing unauthorized use of a stolen or lost cellular phone, by using an IC card.
Further, for example, Patent Document 2 discloses a method of preventing information leakage from a cellular phone by using a password.
Furthermore, for example, Patent Document 3 discloses a method of managing address book information by using a server connected to a network, instead of using a cellular phone.
[Patent Document 1] JP 2005-84846 A
[Patent Document 2] JP 2006-67130 A
[Patent Document 3] JP 2007-123959 A